Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates generally to hydraulic cylinders, and more particularly to a hydraulic cylinder monitoring apparatus for a welded construction-type hydraulic cylinder.
2. Description of the Related Art
In general, hydraulic cylinders with operating pressures less than 5000 psi can be grouped into three (3) basic categories: (1) Low Cost Tie-Rod Construction; (2) Welded Construction; and (3) Industrial (Mill Type) Tie-Rod or Threaded Construction. The industrial type cylinders were the first group to actively employ linear transducers due to the nature of their applications. Linear transducers are used to monitor the position and/or movement of a piston or piston rod in a hydraulic cylinder. Since these applications commonly included in-plant equipment, machine tools and highly specialized uses, design of the equipment could be adjusted to accommodate the additional design requirements driven by adding linear transducers and their impact upon form, fit and function of the equipment. hi other words, the equipment could be designed to meet the constraints associated with incorporating a linear transducer into a cylinder.
As programmable Logic Controller (PLC) usage became more cost effective, original equipment manufacturer""s (OEM""s) producing mobile equipment have employed them to improve operator interface requirements (user friendly) as well as automate functions repeatedly used by the equipment. Many functions involved the use of cylinders as linear actuators. The position and movement of these actuators had to be monitored and communicated back to the PLC if closed-loop feedback control was to be utilized. Cylinders were capable of providing this feedback via the output of linear transducers. Placing the transducers inside cylinders inside of tie-rod or threaded construction hydraulic cylinders have provided the most direct method of incorporating them as well as protecting them from damage and environmental degradation.
As the majority of cylinders used in mobile equipment are of the welded construction type, the challenge has been to find a way of installing a linear transducer into a welded cylinder tube and provide access for serviceability and troubleshooting. Incorporating cylinders with transducers into mobile equipment creates additional challenges. The cylinder needs to be designed for the equipment rather than modifying the equipment design to accept the cylinder. Moreover, the ability to retrofit/upgrade existing equipment without extensive structural change requires direct interchangeability between xe2x80x9csmartxe2x80x9d and xe2x80x9cdumbxe2x80x9d cylinders which adds further design constraints. Consequently, before the present invention, there existed a need to solve the aforementioned problems.
The present invention relates to a hydraulic cylinder monitoring apparatus of a type having a tube with a first end and a second end and a removable first cap member for selectively closing the first end of the tube, the first cap member having a first opening therein. A second cap member is welded to the other end of said tube, the second cap having a second opening therein. A piston is sealingly disposed within the tube for movement between a first and a second position between the first and second ends of the tube. A rod is operatively attached to the piston and extends from the piston and through the first opening in the first cap member whereby the piston and rod can move together between the first and second positions.
A first hydraulic fluid port extends into the tube adjacent said one end of the tube. A second hydraulic fluid port extends into the tube adjacent the second end of the tube. A supplemental cap is removably attached to the second cap member, the supplemental cap having a passageway therein. A transducer, including an elongated portion is removably fixed with respect to the supplemental cap, and a follower member is removably fixed with respect to said piston whereby when the piston moves, the follower member moves along the elongated portion of the transducer.
Electrical wires are attached to and lead from the elongated portion of the transducer, the wires extending through the passageway in said supplemental cap whereby the position of the piston can be monitored with respect to the supplemental cap by using the transducer to sense the position of the follower member.
An object of the present invention is to provide a welded construction type hydraulic cylinder with an apparatus for monitoring the position of the piston and/or piston rod of the hydraulic cylinder.
Another object of the invention is to provide a diagnostic device for helping to determine if an electrical problem is in a transducer of a monitoring system or in the wiring leading thereto.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.